Electronic device

ABSTRACT

A transistor structure is configured as a vertical type transistor. The transistor structure has a patterned electrode located between a gate electrode and a channel region of the transistor structure. The patterned electrode has one or more regions of discontinuity of the electrode. The patterned source electrode has at least two layers having at least a first and second barriers for injection of charge carriers into the channel region. The patterned electrode is configured such that a second layer having a second, higher, barrier for injection of charge carriers is configured to provide a physical barrier for flow of charge carriers from the electrode into the channel region.

TECHNOLOGICAL FIELD

The invention is in the field of structured electrodes for electronicdevices, and is particularly useful for vertical type transistorstructures or diodes.

BACKGROUND

Various types of electronic devices utilize material selection toprovide desired charge transmission and injection properties for properoperation. Typically, charge carriers, such as electrons or holes, maybe injected from a conducting/metallic electrode into semiconductorelements of the device to thereby provide adjustable electrictransmission properties for applications such as switching, currentrectifying, etc.

Generally, two main types of conductor-semiconductor electrical contactare used, Ohmic contact and Shottky contact. The contact behavior isgenerally determined by electrical properties of the metal electrode andthe semiconductor, and at time by geometry or other characteristics ofthe metal-semiconductor junction.

Various electrode structures are known, being configured to providedesired charge injection properties. For example, WO 2010/113,163,assigned to the assignee of the present application, presents anelectronic device, being configured for example as a vertical fieldeffect transistor. The device comprises an electrically-conductiveperforated patterned structure which is enclosed between a dielectriclayer and an active element of the electronic device. Theelectrically-conductive perforated patterned structure comprises ageometrical pattern defining an array of spaced-apart perforationregions electrically conductive regions. The pattern is such as to allowthe active element of the electronic device to be in contact with saiddielectric layer aligned with the perforation regions. A materialcomposition of the device and features of said geometrical pattern areselected to provide a desired electrical conductance of theelectrically-conductive perforated patterned structure and a desiredprofile of a charge carriers' injection barrier along said structure.

General Description

As described above, repeatable selected performance of electronicdevices relies on appropriate control over charge injection propertiesbetween elements of the device. Thus, there is a need in the art for anovel electrode structure capable to provide appropriate tailoring ofcharge injection properties between the electrode and a semiconductorelements being in electrical contact therewith.

The present invention provides an electrode structure, suitable for usein an electronic device and configured to provide desired chargeinjection properties. The electrode structure is configured with atleast two groups of electrode portions where a first group of regions isconfigured with high injection properties (low barrier for injection)and a second group of regions is configured with lower injectionproperties (higher harrier for injection). In this configuration, chargecarriers are typically transmitted from regions of the first group intoan adjacent semiconductor element. Additionally, charge injectionproperties of the electrode structure are adjusted by providing theelectrode structure with a geometrical configuration such that regionsof the second group provide physical or geometrical blockage for chargetransmission from regions of the first group into the semiconductorelement and towards a target element (e.g. to a drain electrode in thecase of diode of transistor structure).

More specifically, the electrode structure is generally made ofelectrode portions comprising electrode portions of at least twomaterials, having first and second different charge injection propertieswith respect to a third (semiconductor) material of the semiconductorelement. The relative arrangement of first and second groups of regions,made of the first and second materials respectively within the electrodestructure, provides that charge carriers injected from regions of thefirst group into the semiconductor element interact with regions of thesecond group before being freely transmitted into the semiconductorelement bulk volume. To this end, the arrangement of the first andsecond groups of electrode portions within the electrode structure causere-absorption of a portion of the charge carriers emitted from regionsof the first group into regions of the second group. This phenomenoneffectively reduces or at least affects the charge injection propertiesof the electrode structure. Therefore, appropriate design of theelectrode structure provides for tailoring of desired charge injectionproperties of the electrode structure which may be different than theactual injection properties of each of the first and second materialsseparately.

To provide the desired geometry, the electrode structure may beconfigured as a patterned electrode structure. More specifically, asurface of the electrode structure may be configured to provide certaindiscontinuity in electrical characteristics therealong. The surface ofthe electrode structure may thus be configured as a non-simply connectedsurface and the electrode structure has holes or missing portions alongits surface.

Thus, according to one broad aspect, the present invention provides anelectronic device comprising an electrode structure located inelectrical contact with a semiconducting element. The electrodestructure is configured with two or more groups of regions/layerscomprising regions of a first group having first charge injectionproperties and regions of a second group having second charge injectionproperties being lower than the first charge injection properties. Theregions of the second group are configured to provide geometricalharrier for injection of charge carriers from regions of the first groupinto the semiconductor element. According to some embodiments, theelectrode structure comprises at least first and second layers, a firstlayer comprising regions of the first group and a second layercomprising regions of the second group. Additionally one or more of thefirst and second layers may be configured as a multi-layered structure,said multi layered structure comprising at least two of a conductinglayer, semiconducting layer, and an insulating layer.

The electronic electrode structure may be configured as a patternedelectrode, comprising one or more regions of discontinuity in electricalconductivity along a surface of the electrode structure. Said one ormore regions of discontinuity of the electrode structure may beconfigured as one or more holes along surface of the electrodes. Theregions of discontinuity of the electrode structure may be configuredsuch that regions of the second group skirts over the edges of theregions of the first group. Generally, at least one region of the secondgroup may cover at least one region of the first group. Alternatively,the regions of the second group may block portions of the regions of thefirst group while leaving certain portions thereof with direct contactto the semiconductor element. According to some embodiments of theinvention, the electrode structure may be configured to havestep-source, tilted edge or curved geometry in at least onediscontinuity region. In the case of a curved geometry, it may be convexor concave.

According to some embodiment, electrode portions of the first groups ofthe electrode structure may be configured from a conducting materialselected from: Li, Ca, Mg, Al, Ag, ZnO, Au. Additionally, electrodeportions of the second group may he configured from a conductivematerial selected from: Al, Ag, Au, MoO3, Pt, Se. Alternatively,material selection for electrode portions of the first and second groupsmay be reversed for use in electrode structure according to the presentinvention configured for transmission of hole (other than transmissionof electrons), thus, electrode portions of the first group may beconfigured from: Al, Ag, Au, MoO3, Pt, Se, and electrode portions of thesecond group may be configured from: Li, Ca, Mg, Al, Ag, ZnO, Au. Theconducting material may also be a doped semiconductor with appropriatelyselected work function.

It should be noted that electrode portions of the first or second groupsmay be multi-layers electrode portions. More specifically, each layer ofthe first and/or second electrode portions may be a multilayeredstructure comprising at least one conducting sub-layer configured of anyone of the materials specified above. Additional layers may comprise aninsulating layer and/or semiconducting layer. Generally, the sub layersmay be arranged such that an insulating sub layer is located between theconducting layers of the first and second electrode portions to therebyprevent current leakage between the electrode portions. Additionally, aninsulating layer may be located at an interface of the electrodeportions of the second groups thereby reducing current transmission atsuch interfaces.

According to some embodiments, the electrode structure may be configuredas a layered electrode structure comprising a first layer being of thefirst group and a second layer being of the second group. The secondlayer is attached to at least one surface of the first layer.

The electronic device utilizing the electrode structure of the presentinvention may be diode or a transistor structure. The electrodestructure may be a source electrode of said diode or transistorstructure. The electronic device may be configured as a vertical typetransistor structure. To this end, the electrode structure may beconfigured as a patterned electrode structure and to be operable as asource electrode. The semiconductor element may be operable as a channelelement of the transistor structure.

According to yet another broad aspect of the present invention there isprovided a transistor structure configured as a vertical typetransistor. The transistor structure comprises a patterned electrodelocated between a gate electrode and a channel region of the transistorstructure. The patterned electrode comprises one or more regions ofdiscontinuity of said electrode, and comprises at least two layershaving at least first and second barriers for injection of chargecarriers into the channel region. The patterned electrode is configuredsuch that a second layer having a second, higher, barrier for injectionof charge carriers is configure to provide a physical barrier for flowof charge carriers from the electrode into the channel region. Accordingto some embodiments, the patterned electrode may be a source electrodeof the transistor structure. Additionally, the patterned electrode maybe configured as a two layered electrode.

According to some embodiments, the patterned electrode may be configuredas a multi layered electrode, comprising at least two layers ofconducting material.

According to some embodiments of the invention, said one or more regionsof discontinuity of the patterned electrode may be configured as one ormore holes along surface of the electrodes, thereby allowing penetrationof electric field generated by the gate electrode into the channelregion.

According to yet another broad aspect, the present invention provides anelectrode structure for use in electronic device. The electrodestructure comprises at least first and second groups of electrodeportions having first and second charge injection propertiesrespectively. Geometrical arrangement of the electrode portions of thesecond group, having lower charge injection properties, is configured toprovide physical barrier for transmission of charge carrier fromelectrode portions of the first group having higher charge injectionproperties.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosedherein and to exemplify how it may be carried out in practice,embodiments will now be described, by way of non-limiting example only,with reference to the accompanying drawings, in which:

FIG. 1 exemplifies a transistor structure utilizing two-layeredpatterned electrode according to the conventional configuration;

FIGS. 2A to 2H exemplify configurations of electronic devices utilizingan electrode structure according to embodiments of the presentinvention, FIGS. 2A-2G illustrate transistor structure configurationsand FIG. 2H illustrates a diode configuration;

FIGS. 3A and 3B exemplify different configurations of the electrodeportions (FIG. 3A) and relative configurations of the electrode portionsat discontinuity regions (FIG. 3B) according to embodiments of thepresent invention;

FIG. 4A to 4C illustrate surface geometry of electrode structureaccording to certain embodiments of the present invention, the electrodestructure is illustrated with circular holes (FIG. 4A), rectangularholes (FIG. 4B) and a bottom view of the electrode having rectangularholes (FIG. 4C);

FIGS. 5A to 5D show simulated source-drain current density for verticaltype transistor structure utilizing conventional Au/Pt patterned sourceelectrode (FIG. 5A), step-source structure Au/Pt electrode according tothe invention (FIG. 5B), conventional Ag/Pt patterned source electrode(FIG. 5C) and step-source structure Ag/Pt electrode according to theinvention (FIG. 5D);

FIG. 6 illustrates a comparison between electronic performance ofconventional patterned Ag/Pt source electrode and step-source Ag/Ptelectrode according to the invention; and

FIGS. 7A and 7B show simulated source-drain current density for verticaltype transistor structure utilizing respectively tilted edge Au/Pt andAg/Pt source electrode according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is made to FIG. 1, illustrating an example of transistorstructure 10 configured as described in WO 2010/113,163 (assigned to theassignee of the present invention). As shown, the transistor structure10 is configured as a vertical type transistor and includes source anddrain electrodes 12 and 16 and a channel region 16 located therebetween.Additionally, the transistor includes a gate electrode 18 located underthe source electrode 12 and separated therefrom by an isolating(dielectric) layer 20. It should be noted that the source and drainelectrodes may be replaced between them.

As shown, the electrode located close to the gate electrode 18, in thisexample the source electrode 12, is patterned to allow electric field topenetrate into the channel region 14 to thereby increase its effect oncharge carrier's mobility through the channel 14. Additionally, thepatterned source electrode 12 is formed of two layers 12A and 12B madeof different materials having selected different charge injectionproperties with respect to the channel region 14. Generally, the bottomportion of the source electrode 12A is made of material having highcharge injection properties and the top portion 12B is made of materialhaving lower charge injection properties.

In this connection it should be noted that charge injection propertiescan generally be defined by the work function or Fermi energy level of aspecific injecting material, relative to the energy level of theaccepting material into which the charge is injected. The lower thedifference in energy level of the materials, the lower the energy gapfor charge carriers to “escape” the material, i.e. transfer from onematerial to the other, and thus the higher the charge injectionproperties and vice versa.

The present invention provides an electrode structure, configured toprovide increased variability of effective charge carriers' injectionutilizing geometrical structure of electrode regions/portions of atleast two groups having different injection properties. This allows finetuning of the effective injection properties of the electrode structurethereby enabling to provide a desired affinity for charge injection.

Reference is made to FIGS. 2A-2H illustrating several configurations ofan electronic device 100 utilizing an electrode structure 120 accordingto the present invention. FIGS. 2A-2G illustrate five transistorstructure configurations and FIG. 2H illustrates a diode configuration.It should be noted that the electrode structure according to the presentinvention is suitable for use in various electronic devices utilizingcurrent transmission from a conducting electrode (e.g. metallic) into asemiconductor element and thus should be interpreted accordingly withrespect to transistor structures, diodes and other electronic devices.

More specifically, the transistor structures 100 illustrated in FIGS.2A-2G are configured as a vertical type transistor structures andinclude a patterned source electrode 120, channel region 140, drainelectrode 160 and a gate electrode 180 being separated from the sourceelectrode 120 and/or the channel region 140 by an dielectric layer 200configured to isolate the gate 180 from the channel 140.

Thus, the electronic device 100, which may be used e.g. as a transistorstructure or as a diode structure, utilizes an electrode structure 120configured with at least two groups of regions 120A and 120B havingfirst and second charge injection properties. More specifically, thefirst and second groups of regions are made of materials havingdifferent work functions, such that a Fermi level of the material ofregions 120A is closer to the relevant semiconductor level (highercharge injection properties) while the difference between Fermi level ofthe material of regions 120B and that of the semiconductor element ishigher providing lower charge injection properties. The electrodestructure 120 is configured such that regions 120B provide a bothphysical (geometric) and electronic barrier for passage of chargecarriers from electrode portions of regions 120A into the volume of thechannel region 140 and towards the drain 160.

As exemplified in FIG. 2A, the electrode structure may be configured asa layered electrode having at least two layers 120A and 120B and may beconfigured as a patterned electrode having regions of discontinuity inelectrical conductivity along its surface. This will be described inmore details below, with reference to FIGS. 3A-3B. Additionally, the toplayer 120B, having low charge injection properties, is configured toskirt over the edges of the bottom layer 120A to thereby causeinteraction with charge carriers emitted from electrode portions 120Ainto semiconductor element 140 (e.g.

channel). This interaction provides effective barrier for chargecarriers passage into the semiconductor element 140 (e.g. channel). Thisstep-source geometry of the electrode structure 120 allows for desiredselection of charge injection properties. Additionally, due to thebetter charge injection properties of the regions of the first group(bottom layer) 120A, which may even provide an Ohmic contact with thesemiconductor element 140, charge carriers will be transmitted into thesemiconductor 140 from these regions rather than from the regions of thesecond group (top layer) 120B. However, the transmitted charge carriersare propagating into the semiconductor elements 140 and are beingdirected towards an electrically conductive element such as the drainelectrode 160. Thus, the physical location of the top layer 120B of thepatterned electrode 120 partially block passage of charge carriers, andeven absorbs a portion of the charge carriers passing nearby, therebyincreasing an effective barrier for charge injection from the patternedelectrode 120.

As indicated above, the top layer 120B (second group) of the electrodestructure may be configured to overflow over the edges of the bottomlayer 120A (first group). Additional configurations may provide anangled cut of edges of the electrode structure at its regions ofdiscontinuity (e.g. holes, edges of electrode regions) as shown in FIG.2B illustrating a tilted face source geometry of the electrode structure120. Alternative, configuration is shown in FIG. 2C, showing anadditional step-source geometry where a portion 142 of the semiconductorelement 140 separates the patterned electrode structure 120 from thedielectric layer 180. This allows higher surface area of electrodeportion 120A to be exposed and used for charge injection into thesemiconductor element 140. It should be noted that in thisconfiguration, charge carriers being injected into the semiconductorelement 140 still pass close to the top electrode portion 120B and aportion thereof may be absorbed therein, thus current transmissionbetween the electrode structure 120 and the semiconductor element 140 isdetermined in accordance with an effective barrier for charge injectiondue to the geometrical configuration of the electrode structure.

Two additional examples of the electronic device 100 and the electrodestructure 120 configurations are shown in FIGS. 2D and 2E. In theseconfigurations, the electrode structure is configured of electrodeportions 120A, having lower barrier for charge injection, being coveredby electrode portions 120B having higher barrier for charge injection.As shown, the injecting electrode portions 120A are configured to havecertain interface region with the semiconductor element 140 to allowcharge injection thereto, while the barrier portions 120B are arrangedsuch as to provide geometric barrier for charge transmission along thesemiconductor element.

Some additional configurations are exemplified in FIG. 2F and 2G. Theseconfigurations of the transistor structure 100 utilize a multi-layerarrangement of at least one of the first or second electrode portions120A or 120B. As shown, the drain 160 is located directly on top of thesecond electrode portion 120B using only the spaces above thesemiconductor channel 140 (FIG. 2F) or located on top of the secondelectrode portion 120B along the structure (FIG. 2G). In suchconfigurations, at least one of the electrode portions is a multi-layerstructure including at least one insulating layer. The insulating layeris located on top of a conducting layer of the electrode. Such multilayered structure is exemplified and described in more details withreference to FIG. 3A.

As indicated above, FIG. 2H exemplifies an electronic device 100,configured as a diode structure (e.g. Schottky diode). The device 100includes an electrodes structure 120 according to the present invention,a semiconductor element 140 being in electrical contact with theelectrode structure 120, and a drain electrode 160 being in electricalcontact with the semiconductor element 140. As shown, the electrodestructure 120 includes two groups of electrode portions, electrodeportions 120A have low barrier for charge injection to the semiconductorelement 140, and electrode portion(s) 120B have higher barrier forcharge injection. It should also be noted that the low-barrier electrodeportions 120A may face the opposite surface of the electrode structure120, however in this configuration, electrode portions 120A should havecontact with the semiconductor element 140 as shown e.g. in FIG. 2E.Additionally, when used as a diode structure (or any other device typesuch as lateral transistor structure) the semiconductor element 140 ofthe electronic device 100 may be formed of one or more layers orsub-layer of semiconductor materials having different electricalproperties. Thus the semiconductor element may be configured to providea gradient of electrical properties to thereby allow desired operationof the device.

As indicated above, various configurations of the electrode portionsand/or interface therebetween may be used to provide the desired chargeinjection properties. Reference is made to FIGS. 3A and 3B exemplifyingconfigurations of the electrode portions (FIG. 3A) and interface betweenthe electrode portions (FIG. 3B). As shown in

FIG. 3A, any one of the first and second electrode portions (generallyat 120) may be a multi-layered structure. Such multi layered structuremay include two or more layers including at least one layer ofelectrically conducting material 124, and may include additional layersof insulating and/or semiconducting materials. As exemplified in thefigure a multi layered structure may include a first conducting layer124, a second semiconducting layer 126 and a third insulating layer 128.It should be noted that a sequence of these sub-layers is generallyselected in accordance with fabrication demands as well as desiredelectronic properties of the device. The sub-later sequence may alsovary to fine tune the multi-layer properties. Alternatively, the multilayered structure may be a bi-layer structure having a first conductinglayer 124 and a second insulating layer 128. This provides insulatingbetween the first and second electrode portions and/or between thesecond electrode portion and the channel (or the drain electrode asshown in FIG. 2G).

FIG. 3B illustrates six variations of interface structure between thefirst and second electrode portions. Interface structures 129A-129C showthat the second electrode portions skirt over the first electrodeportion to provide blocking and re-absorbing of charge carrierstransmitted therefrom. Alternatively, in interface structures 129D-129Fthe second electrode portions are configured to allow direct chargecarriers' transmission from the first electrode portions and into thechannel region. It should he noted that such interface structure mayprovide additional current transmission and may be used for propertailoring of transmission propertied of the transistor structure to meetthe desired properties.

Reference is made to FIGS. 4A-4C illustrating a top and bottom views oftwo configurations of the patterned electrode structure 120. Asdescribed above, the electrode structure is configured such that asurface of the electrode facing the direction of preferred chargecarriers' propagation within the electronic device is not a simplyconnected surface. Thus, the electrode structure 120 has structuraldiscontinuity along its surface. As shown, the electrode structure 120has one or more regions of discontinuity 122 along its surface. Theseregions may be of any geometrical shape, circular regions areexemplified in FIG. 4A and rectangular regions are exemplified in FIG.4B, and may be arranged in an ordered or disordered fashion along thesurface of the electrode 120. It should however be noted that anygeometrical arrangement of discontinuity regions may be suitable for thepresent invention. However injection of charge carriers into thesemiconductor element 140 may be affected by relative interface area ofelectrode portions 120A and the semiconductor element as well as aneffective trajectory for passage of charge carriers away from theelectrode structure 120.

FIG. 4C exemplifies the electrode structure 120 configuration withrectangular regions of discontinuity, from the side thereof that facesthe dielectric layer 180. As shown, at the edges of discontinuityregions 122, the top layer 120B overflows, and skirts over the bordersof the bottom layer 120A. This limits the effective area for chargeinjection, as well as provides a physical/geometric harrier for chargecarriers' passage towards the volume of the semiconductor element 140and the drain electrode 160.

Reference is made to FIGS. 5A-5D showing simulated charge transfercharacteristics in a transistor structure having a conventional twolayered source electrode and a structure source electrode according tothe present invention. FIGS. 5A-5C show current density J_(p) along thesemiconductor element 140 with respect to gate voltage V_(G). FIGS. 5Aand 5B show respectively transfer properties of Gold (Au)/Platinum (PT)layered source electrode having a flat face structure as illustrated inFIG. 1 and having a step-source electrode structure as illustrated inFIG. 2A; FIGS. 5B and 5C show such transfer properties for Silver(Ag)/Platinum (Pt) layered source electrode having flat-face structureand step-source structure. Each of these graphs shows three measuredplot line G1-G3 for drain electrode bias of 1V, 2V and 3V respectively.

In these figures, the Gold (Au) or Silver (Ag) are used as the materialshaving low barrier for charge injection, and thus are used at the bottomportion 120A of the electrode structure 120. This is while Platinum (Pt)is used as the low injection material (high barrier) and is thus usedfor the top portion 120B of the electrode structure 120. Additionally,as shown, the use of step-source geometry exhibits higher barrier forcurrent flow through the transistor under similar voltage conditions.Additional comparison is presented in FIG. 6, showing plot G1 and G3from FIGS. 5C and 5D on the same graph. More specifically, FIG. 6 showsplots G1A and G1B respectively measuring current density as a result ofgate voltage for flat and step-source structures of Silver/Platinumelectrode under source-drain voltage of 1V; and similar plots G3A andG3B under source-drain voltage of 3V. As can be seen, increasing thesource-drain voltage from 1V to 3V increases the current for zero gatevoltage for flat face geometry (G1A and G3A), but not for thestep-source geometry (G1B and G3B). Additionally, for the highersource-drain voltage, the electrode structure of the present invention(step-source geometry), due to its modified injection properties,requires higher gate voltage (2V) to reach its maximal current while theconventional electrode reaches the maximal current at gate voltage of1V. Thus, the electrode structure of the present invention provideshigher ON/OFF voltage ratio and potentially also higher gate bias toreach its maximal current density output. This is similar to providingof lower injection properties material as the source electrode, orproviding the source electrode with higher barrier for charge injection.It should be noted however, that unlike the case of changing the sourcematerial, the use of an electrode structure according to the presentinvention for injection properties' tuning eliminates, or at leastsignificantly reduces penalty in the maximum current supported by theelectronic device.

The tilted-face geometry of the electrode structure, exemplified in FIG.2B provides substantially similar current density dependence withrespect to the source-drain voltage and the gate voltage. This isexemplified in FIGS. 7A and 7B showing similar measure results forgold/platinum and silver/platinum source electrode having a tilted-faceedge structure. As shown, for higher source-drain voltage, thetransistor structure requires higher gate voltage to reach its maximalcurrent density and thus provides higher ON/OFF voltage ratios withrespect to the conventional flat-face electrode geometry.

In this connection it should be noted that the electrode structureaccording to the present invention may be configured for operation istransmission of charge carriers being either electrons (e⁻) or holes(h⁺). Additionally, the electrode portions of the first and secondgroups are generally selected in accordance with preferred chargecarriers to be transmitted by the electronic device. To this end, forelectrode structure configured for transmission of electrons throughsemiconducting element (utilizing the LUMO level thereof), the materialof the electrode portions of the first groups (i.e. having low barrierfor charge injection) may be selected from the following list ofmaterials: Li, Ca, Mg, Al, Ag, ZnO and Au. Additionally, the electrodeportions of the second group (having higher barrier for chargeinjection) may be configured of a material selected from the followinglist of materials: Al, Ag, Au, MoO3, Pt and Se. For the electrodestructure, configured for transmission of holes (electron vacancies)through the semiconductor element (utilizing the HOMO level thereof),the material for electrode portions of the first group may be selectedfrom the following list of materials: Al, Ag, Au, MoO3, Pt and Se. Inthis configuration, the electrode portion of the second group may bemade from any one of the following materials: Li, Ca, Mg, Al, Ag, ZnOand Au. It can be appreciated that generally, the materials suitable foruse for electrode portions of the first and/or second groups may bereplaced if the electrode is configure for transmission of electrons orholes through the corresponding levels of the semiconductor element. Theportions of the electrode of the first or second group may be acombination of metals and may be provide with additional layers tooptimize materials' compatibility along with injection properties. Itshould be noted that additional material may be used, although notspecifically described herein.

Generally the transistor structure as described above may be produced inany lithography method. Additionally various printing methods may beused to produce the transistor structure of the present inventions. Forexample, the structure, or at least one or more layers thereof, may beproduced by injection printing method.

Thus, the present invention provides novel electrode structure, suitablefor use in electronic devices such as transistor structure (e.g.vertical type transistor structure, thin film transistor etc.), assemiconductor diode or any other suitable electronic device. Theelectrode structure is configured to provide a physical patternproviding an effective barrier for charge carriers' passage through thedevice. Thereby enabling control over device properties which issignificantly higher than by material selection. Those skilled in theart will readily appreciate that various modifications and changes canbe applied to the embodiments of the invention as hereinbefore describedwithout departing from its scope defined in and by the appended claims.

1. A transistor structure configured as a vertical type transistor andcomprising a patterned electrode located between a gate electrode and achannel region of the transistor structure, the patterned electrodecomprises one or more regions of discontinuity of said electrode, saidpatterned source electrode comprises at least two layers having at leasta first and second barriers for injection of charge carriers into thechannel region, wherein, the patterned electrode is configured such thata second layer having a second, higher, barrier for injection of chargecarriers is configure to provide a physical barrier for flow of chargecarriers from the electrode into the channel region.
 2. The transistorstructure of claim 1, wherein said patterned electrode is a sourceelectrode of the transistor structure.
 3. The transistor structure ofclaim 1, wherein said patterned electrode is configured as a two layeredelectrode.
 4. The transistor structure of claim 1, wherein saidpatterned electrode is configured as a multi layered electrode,comprising at least two layers of conducting material.
 5. The transistorstructure of claim 1, wherein said one or more regions of discontinuityof the patterned electrode are regions of discontinuity in electricalconductivity along said patterned electrode.
 6. The transistor structureof claim 1, wherein said one or more regions of discontinuity of thepatterned electrode being configured a one or more holes along surfaceof the electrodes, thereby allowing penetration of electric fieldgenerated by the gate electrode into the channel region.
 7. Thetransistor structure of claim 1, wherein at least one of the first andsecond layers is configured as a multi-layered structure, said multilayered structure comprising at least two of a conducting layer, asemiconducting layer, and an insulating layer.
 8. The transistorstructure of claim 1, wherein said one or more regions of discontinuityof said patterned electrode are configured such that the second layer ofthe patterned electrode skirts over edges of the first layer of saidpatterned electrode at edges of said regions of discontinuity.
 9. Thetransistor structure of claim 1, wherein at least one region of thepatterned electrode, the second layer thereof covers the first layer.10. The transistor structure of claim 8, wherein the patterned electrodeis configured to have at least one of the following configurations:step-source edge geometry, tilted edge geometry and curved edge geometryin at least one discontinuity region.
 11. The transistor structure ofclaim 1, wherein the first layer comprises a conducting materialselected from: Li, Ca, Mg, Al, Ag, ZnO, Au, and the second layercomprises a conductive material selected from: Al, Ag, Au, MoO₃, Pt andSe.
 12. The transistor structure of claim 1, wherein the first layercomprises a conducting material selected from: Al, Ag, Au, MoO₃, Pt, Se,and the second layer comprises a conductive material selected from: Li,Ca, Mg, Al, Ag, ZnO and Au.
 13. The transistor structure of claim 1,wherein the first and second layers of said patterned electrode areconfigured with electronically conductive materials having selectedfirst and second charge injection properties.